Low Water Levels in the Marsh
Water levels within the marsh fluctuate.
I am sure you have noticed the low water levels in the marsh this past fall. We have been receiving comments and questions recently, expressions of surprise and wonder. On closer inspection you also may have noticed the fairly large number of Canada Geese, Great Blue Herons, Egrets and a number of Trumpeter Swans hanging out in the marsh. Good observations, and they are connected.
The short explanation of the first observation is that the extensive muddy flats and edges you see are the result of little or no rain. The La Crosse Tribune reported on October 11th last year that thirteen counties in west central Wisconsin were experiencing drought or “severe” drought at the beginning of this month. Jackson and Trempealeau counties had received little or no rain this summer. The Tribune (10/18/22) reported that here in La Crosse we are six inches below annual average rainfall levels. John Sullivan, a member of our board who conducts regular water level measurements, reports that the water level in the easternmost cell of the marsh (east of the Cottonwood Trail) was the lowest since 2016. It’s in the middle or western cells of the marsh where we see the most dramatic effects of his measurements – mud flats and isolated pools.
Here's a few things to keep in mind. Our experience here in La Crosse in the past many years in the water department has been dominated by high water – extreme storms, more rain each year, street flooding, closed trails in the marsh, and a wetland that looks like a lake. All the product of climate change. But, as great parts of the nation will attest, drought is also a part of the story. Little to no rain and greater rates of evaporation. A warmer atmosphere increases evaporation. Dry, wet there is no new normal.
One of our three goals in the long-range marsh restoration project now in progress is to re-establish the flow of water from east to west through the marsh. Wetlands serve to store and slow down flood waters but shouldn’t just stop the water and pool it, resulting in consistent and long-term high-water levels. Our trails too often serve as dams. With some changes to the trails, to culverts under the trails, we aim to establish a hydrology regime that returns seasonal changes to the marsh. Low water like we are experiencing now will be more common – not ever present, but common. Why?
Seasonal low water is good for habitat, a second goal of the marsh restoration project. It’s good for the wading birds and the bottom feeding birds because they can reach the bottom. It allows the growth of emergent vegetation, along now exposed edges and muddy flats. With lower water levels we have witnessed the appearance of healthy stands of wild rice in the marsh this summer. Some of it seeded three years ago but most we didn’t seed at all. Current conditions favor emergent vegetation. Finally, and obviously, low water is good when we get the next thunderstorm. The marsh can better do its work.